elm: Major cleanup of EO files

elm: Major cleanup of EO files

This prevents legacy EO classes from being exposed through .eo.h headers
or .eo in share/eolian/includes. Also removes a slew of useless xxx_eo.h
intermediate headers.

Notes:
 - elm_systray has no proper API: it's not clear if the EO API should be
   released (in which case it needs to be renamed to efl_something) and
   there is no legacy API to create a systray object.
 - Some files have been placed in a "FIXME" section, as I believe they
   are necessary within EO land, but at the same time still don't
   conform to the interfaces (eg. name starts with elm_).
 - elm_interface_scrollable is required by photocam. This means photocam
   needs to be adapted to fit the EO scroller API (still to be
   completed, I believe).

Bugs:
 - This breaks most C++ examples. I KNOW. And I'm working on it.

Ref T5301